The invention relates to a vehicle-sensitive sensor for a belt retractor for vehicle safety belt systems.
Belt retractors are widely known components of vehicle safety belt systems. The retractors have a belt spool rotatably mounted in a frame and a blocking mechanism in order to block the belt spool against an unwinding of belt webbing in the case of an impact of the vehicle. The blocking mechanism is controlled by means of the vehicle-sensitive sensor responding to accelerations of the vehicle. Known vehicle-sensitive sensors have a coupling pawl in the form of a one-sided lever, under which a steel ball is arranged. The coupling pawl lies on the steel ball with a depression in the form of a spherical segment. If an intense acceleration occurs in the case of a vehicle impact, then the steel ball moves so that the depression in the form of a spherical segment and hence the coupling pawl are raised. The vehicle-sensitive sensor is arranged here beneath the clutch disc, so that on raising the coupling pawl, the end of the latter is guided into the clutch toothing and hence the blocking mechanism is activated. Conventional vehicle-sensitive sensors are only adaptable in a limited manner to various arrangements in the belt retractor. A further disadvantage of conventional vehicle-sensitive sensors lies in that an installation of the belt retractor which is inclined with respect to the structurally given installation position is not possible, because the gravity then engaging obliquely on the steel ball causes a permanent displacement of the steel ball Connected with a permanent blocking of the belt spool.
Through the invention, a greater flexibility is to be achieved with the arrangement and construction of the vehicle-sensitive sensor for a belt retractor. This is achieved in a sensor which comprises an inertia body displaceable in case of decelerations and accelerations of the sensor, and a two-armed lever. A first arm of the two-armed lever forms a coupling pawl, and a second arm of the two-armed lever is able to be engaged by the inertia body such that, in case of a displacement of the inertia body, the lever is pivoted so that the coupling pawl is directed into a clutch toothing. The provision of a two-armed lever makes possible a substantially more flexible construction of the vehicle-sensitive sensor compared with the prior art. Thus, for example, the distance covered by the end of the coupling pawl, the size and weight of the inertia body and the spatial arrangement of the inertia body in the belt retractor can be easily varied, without having to accept restrictions in the operating reliability.
As a further step, provision is made that the sensor has a housing on which the lever and the inertia sensor are mounted and which is arranged in relation to a reference so as to be pivotal about an adjustment axis, with a nose of the coupling pawl, able to be guided into the clutch toothing, lying on the adjustment axis. Such a construction of the vehicle-sensitive sensor provides the precondition for an adjustment of the vehicle-sensitive sensor on differently inclined installation positions of the belt retractor. The sensor can be pivoted as a unit in the belt retractor, without its release values, i.e. the values which are necessary for a displacement of the inertia body, or the distance covered on displacement of the inertia body from the nose of the coupling pawl changing. Furthermore, the installation angle of inclination may now be adjusted in a simple manner.
In further development of the invention, provision is made that the nose of the coupling pawl, able to be directed into the clutch toothing, a point on the rotation axis of the lever, and the center of gravity of the inertia body lie on the adjustment axis in the state of rest of the sensor. Thereby, a compact sensor unit results, which only has a small space requirement on a rotation about the adjustment axis.
Advantageously the housing is provided with an adjustment cylinder, which is rotatably arranged. The sensor can be arranged for example in a bore of a covering hood before its being fastened to a frame of a belt retractor. An adjustment cylinder also makes possible a rotatable arrangement of the sensor which is simple to produce and in so doing reliable in operation.
Furthermore, provision is made that a display- and adjustment device is provided for the pivot position of the housing in relation to the clutch disc. Owing to these steps, a single type of belt retractor can be adjusted to various installation inclinations, for example for various vehicle types. The display- and adjustment device can be arranged here such that the adjustment can be carried out and detected from the exterior.
Provision is made that the second arm of the lever lies against the inertia body in the state of rest of the sensor. Each displacement of the inertia body is thereby converted directly into a movement of the coupling pawl, whereby a rapid response of the sensor is achieved. As the second arm of the lever lies against the inertia body, in driving operation also no rattling of the lever can occur.
Alternatively, provision is made that the second arm of the lever in the state of rest of the sensor is arranged at a predetermined distance from the inertia body. Here, it is advantageous that the initial displacement of the inertia body is not influenced by friction between the second arm of the lever and the inertia body. The exact adherence to the structurally given acceleration threshold, after which a displacement of the inertia body takes place, is thereby ensured.
As a further step, provision is made that the sensor has a housing with a stop in which an arm of the lever abuts in the state of rest. In this way, a constant predetermined distance can be ensured between the arm of the lever and the inertia body.
It is advantageous if the inertia body is formed by a ball and the second arm has a ring which surrounds a segment of the ball. The provision of a ring which surrounds a segment of the ball makes it possible that the second arm of the lever engages in the lower region of the ball, in which region the ball also sits on a support. Thereby, further design possibilities are opened up for the vehicle-sensitive sensor.
It is advantageous here that the ring has a contact surface facing the ball, which contact surface has substantially the form of a circular conic frustum surface, the generatrix of which is inclined to the central axis of the ring about an angle of approximately 40xc2x0. Such a construction of the ring makes possible a low-friction running of the ball onto the ring, so that the acceleration values necessary for guiding the coupling pawl are only negligibly influenced by friction between ball and ring.
It is advantageous if the sensor has a housing with a bearing support to support the lever and a ball support to receive the ball. The ball support is formed here advantageously by a circular cylinder with a conical depression in an end face, so that an annular support surface is produced for the ball. Through an annular support surface, the ball remains at rest as long as an acceleration value given by the structural design is not exceeded. As only an annular surface is in contact with the ball, the ball support is not liable to contamination.
In further development of the invention, the lever can have at least one bearing edge or two bearing points along its rotation axis. These constructions both make possible a low-friction bearing of the lever and, in so doing one that is simple to produce for example by injection molding. Bearing edges can be mounted in a V-shaped depression, whereas bearing points can be constructed in a conical shape and arranged in likewise conical depressions with a greater taper angle than the bearing points.
In an embodiment of the invention, provision is made that the ring arranged on the second arm of the lever is arranged beneath the central point of the ball. A displacement of the ball thereby leads to a downward movement of the second arm and an upward movement of the coupling pawl, so that the sensor can be arranged beneath the clutch disc of the belt retractor. It is advantageous here if the center of gravity of the lever in relation to the rotation axis of the lever lies on the side of the first arm. The ring is thereby urged by gravity in the direction of the ball, so that in the state of rest of the sensor, the abutment of the ring against the ball or, in connection with a stop, a constant distance of the ring from the ball is ensured.
Alternatively, provision is made that the ring arranged on the second arm of the lever is arranged above the central point of the ball. Here, a displacement of the ball leads to an upwards movement of the second arm and a downward movement of the coupling pawl, so that a sensor with these features can be arranged above the clutch disc. In order to ensure also here a constant distance from the ring to the ball or an abutment of the ring against the ball, the center of gravity of the lever in relation to the rotation axis of the lever advantageously lies on the side of the second arm.